Traditionally, an elevator machinery consists of a hoisting motor which, via a gear, drives the traction sheaves around which the hoisting ropes of the elevator are passed. The hoisting motor, elevator gear and traction sheaves are generally placed in a machine room above the elevator shaft. They can also be placed beside or under the elevator shaft. Another known solution is to place the elevator machinery in the counterweight of the elevator. Previously known is also the use of a linear motor as the hoisting machine of an elevator and its placement in the counterweight.
Conventional elevator motors, e.g. cage induction, slip ring or d.c. motors, have the advantage that they are simple and that their characteristics and the associated technology have been developed during several decades and have reached a reliable level. In addition, they are advantageous in respect of price. A system with a traditional elevator machinery placed in the counterweight is presented e.g. in publication US 3101130. A drawback with the placement of the elevator motor in this solution is that it requires a large cross-sectional area of the elevator shaft.
Using a linear motor as the hoisting motor of an elevator involves problems because either the primary part or the secondary part of the motor has to be as long as the shaft. Therefore, linear motors are expensive to use as elevator motors. A linear motor for an elevator, placed in the counterweight, is presented e.g. in publication US 5062501. How ever, a linear motor placed in the counterweight has certain advantages, e.g. that no machine room is needed and that the motor requires but a relatively small cross-sectional area of the counterweight.
The motor of an elevator may also be of the external-rotor type, with the traction sheave joined directly with the rotor. Such a structure is presented e.g. in publication US 4771197. The motor is gearless. The problem with this structure is that, to achieve a sufficient torque, the length and diameter of the motor have to be increased. In the structure presented in US 4771197, the length of the motor is further increased by the brake, which is placed alongside of the rope grooves. Moreover, the blocks supporting the motor shaft increase the motor length still further.
Another previously known elevator machine is one in which the rotor is inside the stator and the traction sheave is attached to a disc placed at the end of the shaft, forming a cup-like structure around the stator. Such a solution is presented in FIG. 4 in publication US 5018603. FIG. 8 in the same publication presents an elevator motor in which the air gap is oriented in a direction perpendicular to the motor shaft. Such a motor is called a disc motor or a disc rotor motor. These motors are gearless, which means that the motor is required to have a slow running speed and a higher torque than a geared motor. The required higher torque again increases the diameter of the motor, which again requires a larger space in the machine room of the elevator. The increased space requirement naturally increases the volume of the building, which is expensive.